This invention relates to an illumination system and an optical processing apparatus using the same. More particularly, the present invention is suitably usable in a microprocessing procedure wherein coherent light of a linear beam is projected to a workpiece to produce therein, for example, a pattern of a periodic structure having plural openings during the manufacture of an orifice plate for use in a ink-jet type printer.
The optical processing technology using coherent light such as light from an excimer laser, for example, has been used in many applications together with mechanical processings or chemical-reaction applied processings, for example. Particularly, in accordance with recent technology renovations, conditions such as material, optical technology, and production technology, for example, are well-ordered, and the optical processing procedure based on coherent light is used frequently in the field of microprocessing.
Many types of optical processing apparatuses have been proposed for production of an orifice plate, by using laser processing on the basis of a mask projection method. As regards an illumination optical system (illumination system) for use in such optical processing apparatuses, a Koehler illumination system has been proposed in an attempt to illuminate a mask uniformly. Further, there are many other proposals for an illumination optical system wherein, for illuminating a mask with linear light, a Koehler illumination system is defined with respect to a lengthwise direction of the mask while a critical illumination system is defined with respect to a widthwise direction thereof. U.S. Pat. No. 4,733,944 proposes an optical system wherein a pair of orthogonal cylindrical lenticulars are used to vary an illumination region upon the surface of a workpiece. Japanese Laid-Open Patent Application No. 257770/1996 proposes a structure wherein optical systems, which are independent from each other are disposed in relation to a lengthwise direction and a widthwise direction, are provided to illuminate a mask.
In these illumination systems, laser light is directly collected with respect to the widthwise direction. This causes an inconvenience that the processing phenomenon changes if the position of the mask with respect to the widthwise direction changes. The illumination system using orthogonal cylindrical lenticulars as proposed in U.S. Pat. No. 4,733,944 mentioned above, has no concern about the operation in a region where the aspect ratio of the illumination range (i.e., the ratio regarding the lengthwise direction and the widthwise direction thereof) is not less than 50 and not greater than about 90. Further, in the two orthogonal directions, the same illumination method is used. That is, by changing the interval between the pair of orthogonal cylindrical lenticular lenses, the illumination range upon the surface to be illuminated is changed without changing the aspect ratio. In the structure of U.S. Pat. No. 4,733,944, therefore, it is not attainable to change the illumination range only in one direction, that is, horizontal direction or longitudinal direction on the surface to be illuminated. Thus, the aspect ratio can not be changed.
It is an object of the present invention to provide an illumination system and/or an optical processing apparatus using the same, by which an illumination region can be illuminated uniformly and by which the illumination region can be changed only in one direction to thereby change the aspect ratio, such that a workpiece can be processed more easily and more precisely.
In accordance with an aspect of the present invention, there is provided an illumination system for illuminating a particular surface, to be illuminated, with light from a light source, the illumination system including a first optical component having an optical power with respect to a predetermined plane and a second optical component having an optical power with respect to the predetermined plane. The particular surface is illuminated through Koehler illumination with respect to a plane orthogonal to the predetermined plane and is illuminated approximately through critical illumination with respect to the predetermined plane. The first and second optical components are adapted to provide an afocal system and the condition for the afocal system is disconnected when a relative position between the first and second optical components is changed, whereby an illumination range with respect to the predetermined plane, upon the particular surface, is changed.
In accordance with another aspect of the present invention, there is provided an optical processing apparatus including illumination means including an illumination system as recited above, for illuminating a mask having a pattern and projection means for projecting the illuminated pattern of the mask onto a substrate, for processing the same.
In accordance with a further aspect of the present invention, there is provided a method of manufacturing an orifice plate, including the steps of loading a substrate in an optical processing apparatus as recited above and illuminating a mask having a plurality of openings arrayed along a certain direction, so that the pattern is projected onto the substrate to produce plural openings therein.
In accordance with a yet further aspect of the present invention, there is provided an ink-jet printer including an orifice plate as produced in accordance with an orifice plate manufacturing method as recited above.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.